1. Field of the Invention
This invention relates to analyte sensors such as glucose sensors used in the management of diabetes and methods and materials for making such sensors, for example nanostructured electrode materials.
2. Description of Related Art
Analyte sensors such as biosensors include devices that use biological elements to convert a chemical analyte in a matrix into a detectable signal. There are many types of biosensors used for a wide variety of analytes. The most studied type of biosensor is the amperometric glucose sensor, which is crucial to the successful glucose level control for diabetes.
A typical glucose sensor works according to the following chemical reactions:
The glucose oxidase is used to catalyze the reaction between glucose and oxygen to yield gluconic acid and hydrogen peroxide (equation 1). The H2O2 reacts electrochemically as shown in equation 2, and the current can be measured by a potentiostat. These reactions, which occur in a variety of oxidoreductases known in the art, are used in a number of sensor designs.
A variety of sensors that incorporate nanostructured electrode materials, for example carbon nanotubes, are known in the art. Illustrative devices include those that use peptide nucleic acid receptors designed to recognize a specific DNA sequence and attached to the surface of silicon nanowires to detect the presence of a DNA sequence through hybridization-induced conductance changes (see, e.g. Hahm and Lieber (2003) Nano Lett. 4:51). Hybridization of a single-stranded DNA probe attached to silicon nanowires with the complementary DNA strand has been detected by conductance changes (see, e.g. Z. In et al. (2003) Nano Lett. 4:245). U.S. Patent Application Nos. 2005/124020 and 2007/0208243 and PCT publication WO 02/48701, describe additional devices that use nanostructured materials to detect analytes including biological analytes. The nanostructured materials in these devices are optionally modified for example by coupling the material with an agent that is designed to bind an analyte, an event which subsequently causes a measurable change in conductance of the electrode. There is a need in the art for additional sensor designs that use nanostructured materials (e.g. glucose oxidase coated nanotubes) to sense analytes by producing or consuming an effector (e.g. hydrogen peroxide) that causes a measurable change in the electrical properties of the nanostructured material.